The very idea of spinning a tale of suspense and high drama over stamp collecting is comical, so Theresa Rebeck's Mauritius is certainly funny. The Sandra Feinstein-Gamm Theatre is staging it through November 21, directed by Rachel Walshe.

Unfortunately, that laughter doesn't drown out the sniggering from the gods of plot logic that usually smile appreciatively down upon the Gamm. The tale is riddled with inconsistencies and unconvincing motivations not explained away by the fact that most of these characters are trying to con one or more of the others. After all, even an amateurish con artist, never mind a seasoned one, is going to be sniffing the air for what doesn't smell right.

Okay. Half-sisters Jackie (Amanda Ruggiero) and Mary (Casey Seymour Kim) have a valuable stamp collection left by their mother, who died without leaving a will. Though older sister Mary had fled the dysfunctional family as a teenager and didn't even return for the funeral, she takes for granted that the stamp album is hers. After all, the deceased grandfather who left it to their mother was on Mary's side of the family, and as a girl she had helped him put the collection together — or so she says.

When this sort of situation happens in real life, the dispute goes to probate and the disputants end up splitting the proceeds of a sale. The ownership sounds straightforward.

But for the sake of dramatics, we have Jackie taking the collection to a tacky coin and stamp shop where the proprietor, Dennis (Jim O'Brien), doesn't even acknowledge her existence when she comes in and spouts a long-winded request for help. "Does this look like Antiques Roadshow to you?" he snarls. Dennis wants $2000 just to look at them; in other words: "Get lost, kid." However, hanging out in the shop is Philip (Steve Kidd), who is expert enough to notice a breathtaking find: two rare 1847 Mauritius "Post Office" stamps, one of the earliest issues ever struck and worth millions. Of course, he tells her they're probably not worth much.

From here on, Jackie in Wonderland is spiraling down the rabbit hole and we're yanked in with her. We too could use the help of hallucinogenic mushrooms to remain credulous. At this point, since Jackie knows the name of the stamps that caused such interest, we would expect her to research their rough value and then run, not walk, to a bank safe deposit box. Later, the con men acknowledge among themselves that she's bound to check out their value.

We are to believe that instead of doing so immediately, Jackie continues to rely on Dennis and Philip, without an armed guard, despite their all but drooling in thievish anticipation. (If you're hoping that she is working on conning them, feel free.)

Our two stamp shop friends bring in an expert philatelist and wealthy collector, Sterling (Richard Donelly), to buy the Mauritius pair. The sinister Sterling not only collects stamps and probably orchids, like in noir novels, but also dabbles in real estate and international arms dealing, according to Dennis. Scary guy. He tempts Jackie with a suitcase full of cash, which would allow her to avoid taxes and auction broker fees; she is expected to forgo millions for immediate satisfaction. ("If she goes online, we are fucked," Sterling says to his conspirators. My cat would have gone online to price the stamps by this point.)

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